An index RMAX expressing the total amount of hepatic cell function is precisely evaluated and used for judging an adaptation to an operation in the domain of liver surgery. The index also helps in comprehending a case of a hepatic disease and to judge any convalescence in the domain of medicine.
In a conventional method of measuring the index RMAX, blood for a blank test is first collected from a testee or patient. Then indocyanine green (hereinafter referred to as ICG) of 0.5 mg/kg is injected into the one antecubital vein within 30 seconds. Then blood samples of 3 to 4 ml are collected from the other antecubital vein after lapses of five, ten and fifteen minutes from starting the injection of the ICG solution. Then, 1 ml of the obtained blood is diluted in a physiological salt solution of 2 ml, and colorimetry is performed through a spectrophotometer with a blank of blood serum for the blank test at a wavelength of 805 nm. Reading (OD) in such colorimetry is plotted on semilogarithmic paper, whereby the ICG concentration from five to fifteen minutes is linearly decreased. Zero-order dye concentration in the blood is obtained from an intersection of a straight line connecting three points and the Y-axis. If a half value period (t1/2) of a specific dye concentration in the blood is thereby obtained, a blood plasma disappearance rate K can be calculated from the following expression: EQU K=0.693/t1/2 (liter/min)
In the aforementioned three-point analysis method, the ICG injection must be performed three times while changing dose quantities. In that case, doses of ICG are considered in various ways. For example, a testee may be dosed with 0.5 mg/kg (patient's weight), 1.0 mg/kg and 5.0 mg/kg of ICG on different days, or measurement may be made with doses of 0.5 mg/kg, 1.0 mg/kg and 2.0 mg/kg. Or, ICG may be injected three times with doses of 0.5 mg/kg, 3.0 mg/kg and 5.0 mg/kg or twice with doses of 0.5 mg/kg and 5.0 mg/kg on different days. Further, the index RMAX may be measured in one day with doses of 0.5 mg/kg, 1.0 mg/kg and 5.0 mg/kg, or ICG may be injected three times on different days with doses of 0.5 mg/kg, 1.0 mg/kg and 2.0 mg/kg.
Blood collection and measurements of ICG concentration are performed similarly to the case of a dose of 0.5 mg/kg, to calculate the blood plasma disappearance rate K. The blood serum is initially diluted six to ten times, since the ICG concentration in blood is extremely high.
A method of calculating the index RMAX will now described.
Values of the blood plasma disappearance rate K with dose quantities of 0.5 mg/kg, 3.0 mg/kg and 5.0 mg/kg, for example, are 0.0568, 0.0376 and 0.0334 respectively. A liver removal ratio R is calculated from K (min.).times.D (mg/kg), and hence:
R=0.0568.times.0.5=0.0284 when the dose quantity is 0.5 mg/kg,
R=0.0376.times.3.0=0.1128 when the dose quantity is 3.0 mg/kg, and
R=0.0334.times.5.0=0.1671 when the dose quantity is 5.0 mg/kg.
Then, the values are plotted as shown in FIG. 21, with the X-axis representing the inverse numbers (1/D:(mg/kg).sup.-1) of the dose quantities and the Y-axis representing the inverse numbers (1/R:(mg/kg/min).sup.-1 of the removal ratios.
The dose of 0.5 mg/kg is plotted as 2.00 on the X-axis and 35.21 on the Y-axis and the doses of 3.0 mg/kg is plotted as 0.33 on the X-axis and 8.86 on the Y-axis, while the doses of 5.0 mg/kg is plotted as 0.20 on the X-axis and 6.00 on the Y-axis. A regression line Y of these three points is obtained as follows: EQU i Y=a+bX=3.1658+16.0366X,
whereby a correlation coefficient r=0.999 is applied. The intersection of the Y-line and the Y-axis shows 1/RMAX and hence the index RMAX is represented by the inverse number of a, as 1/a=0.32 mg/kg/min.
In accordance with a two-point analysis method of 0.5 mg/kg and 5.0 mg/kg, the index RMAX is calculated from a regression line Y=2.7544+16.2278X, applying Lineweaver-Burk plotting, as 0.35 mg/kg/min.
In the aforementioned method of measuring the index RMAX, however, some conditions are required in theory of adaptation, while errors may be caused from various sources in the process of measurement and calculation. For example, impossible minus measurement values are recognized once in a while. Further, when the dose quantity is changed three times for measuring the index RMAX as hereinabove described, intravenous injection must be made fifteen times, blood must be collected four times, and ICG must be injected three times, which imposes undesirable burdens on the patient, while several days are required for the pretesting.